title: Boreal feather mosses secrete chemical signals to gain nitrogen.
abstract: The mechanistic basis of feather moss-cyanobacteria associations, a main driver of nitrogen (N) input into boreal forests, remains unknown. Here, we studied colonization by Nostoc sp. on two feather mosses that form these associations (Pleurozium schreberi and Hylocomium splendens) and two acrocarpous mosses that do not (Dicranum polysetum and Polytrichum commune). We also determined how N availability and moss reproductive stage affects colonization, and measured N transfer from cyanobacteria to mosses. The ability of mosses to induce differentiation of cyanobacterial hormogonia, and of hormogonia to then colonize mosses and re-establish a functional symbiosis was determined through microcosm experiments, microscopy and acetylene reduction assays. Nitrogen transfer between cyanobacteria and Pleurozium schreberi was monitored by secondary ion mass spectrometry (SIMS). All mosses induced hormogonia differentiation but only feather mosses were subsequently colonized. Colonization on Pleurozium schreberi was enhanced during the moss reproductive phase but impaired by elevated N. Transfer of N from cyanobacteria to their host moss was observed. Our results reveal that feather mosses likely secrete species-specific chemo-attractants when N-limited, which guide cyanobacteria towards them and from which they gain N. We conclude that this signalling is regulated by N demands of mosses, and serves as a control of N input into boreal forests.
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bay
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Nurun
authors.initials: N
authors.lastname: Nahar
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Oubre
authors.affiliation: Department of Geosciences, Swedish Museum of Natural History, Box 50007, Stockholm, Sweden.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Whitehouse
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: David A
authors.initials: DA
authors.lastname: Wardle
authors.affiliation: The Institute for Subarctic Landscape Research, SE-930 90, Arjeplog, Sweden.
authors.forename: Olle
authors.initials: O
authors.lastname: Zackrisson
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Marie-Charlotte
authors.initials: MC
authors.lastname: Nilsson
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Ulla
authors.initials: U
authors.lastname: Rasmussen
mesh_terms: D001692:Biological Transport; D019068:Bryopsida / Q000382:microbiology / Q000502:physiology*; D009584:Nitrogen / Q000502:physiology; D058458:Nitrogen Cycle; D009586:Nitrogen Fixation; D046937:Nostoc / Q000502:physiology*; D015398:Signal Transduction; D013559:Symbiosis; D014197:Trees
chemical_list: D009584:Nitrogen
keywords: chemo-attractance; cyanobacteria; feather mosses; hormogonia; nitrogen transfer; symbiosis